With reductions in the sizes of electronic instruments, reductions in the sizes and thicknesses of conductive members used in the electronic instruments have also been demanded. There have also been many instruments having foldable structures in notebook-sized personal computers, tablets, portable game machines, and the like. In such cases, conductive members corresponding to folded structures have been used; however, the maintenance of conductivity has been difficult when the conductive members have been repeatedly bent. In particular, reductions in the sizes and thicknesses of instruments have caused the maintenance of conductivity to be precluded with decreasing the bend radii of bends.
Flexible printed circuit boards (FPCs) have been conventionally used in instruments imparted with conductivity across bends. However, there has been a problem that the bending of the FPCs at an acute angle at a bend radius of 0.5 mm or less has caused the resin films of base materials to be ruptured.
Patent Literature 1 describes that an inhibition film that inhibits the curvature radius of a bend from decreasing is disposed on the inside of the bend of a flexible printed circuit board. In such a method, the thickness of the flexible printed circuit board is partly increased, thereby precluding reductions in the size and thickness of an instrument. Moreover, there is a problem that bending cases the periphery of a bend to become bulky because a bend radius is inhibited from decreasing.